Fitts' Law has been established as a robust and pragmatic motor control principle and it has been used in a multitude of applications including ergonomics, human machine interfaces (HMIs), human-computer interactions (HCIs), and rehabilitation. Most applications of Fitts' Law are limited to understanding the relationship of movement time duration, amplitude and precision in the context of arm and hand movements of the upper extremity. In the development of HCI and the design of user interfaces robust eye tracking and detection are thought to play a crucial role. Prior to his seminal publication in 1954, Fitts et al. published a 1950 study on the eye movements of aircraft pilots during instrument-landing approaches. Since that time and up until 2003, Fitts et al. eye movement study was only cited 16 times, whereas Fitts' Law had been cited 855 times. Typically coupled with eye movement, head movement has also been found to be an effective, simple, and natural way of pointing to objects, communication, and interaction.
More recently, various studies have used Fitts' Law to quantify or evaluate head and neck movements related to two main purposes: 1) as an input control signal for rehabilitative/assistive technology designed for use by quadriplegic patients; or 2) to understand the effect of a condition, e.g. age, neck pain, tension type headache, etc. or a rehabilitative intervention on performance. The linear relationship between the index of difficulty and head movement time has been substantiated in each of these latter studies that were designed to assess the effect of various conditions or rehabilitative interventions on performance.
From a functional assessment perspective, several approaches and methods are available to the rehabilitation practitioner or clinician to evaluate neck pain and monitor a patient's progress and response to treatment, such as passive and active range of motion (ROM), muscle strength and endurance, and joint position sense. Although some of these functional assessment measures have been shown within the literature as having high to moderate reliability in terms of distinguishing different types of neck pain patients from each other and from controls, others such as joint re-positioning and muscle strength and endurance have been shown to be less efficacious attempts to quantify the kinesthetic deficits associated with neck pain. Several approaches to measure head-repositioning have been applied. Presently, the ability of these tests in being able to discriminate between patients with whiplash associated disorders and chronic neck pain from controls has not been fully established. It has been suggested that these tests may be affected by motivational factors and are not necessarily always performance based.
In a systematic review of the literature of patients with chronic, idiopathic neck pain, it was identified that there is a paucity of studies and that there were relevant limitations associated with evaluating complex or postural repositioning tests that did not permit any solid conclusions about them. However, the ability of head-to-neutral repositioning tests to consistently distinguish between-study and between-subgroup effects was found and suggests that people with chronic, idiopathic neck pain have poorer performance than asymptomatic controls. In 8 of the 13 studies included in the systematic review, 6 research articles made reference to a test-retest reliability methodology and 2 studies assessed a novel approach to using joint position sense to evaluate cervicocephalic proprioception using a test-retest approach. Empirically, the importance of determining the reliability of a tool or measure prior to its implementation in a clinical setting cannot be overstated. This is particularly true for rehabilitation practitioners and clinicians who rely on evidence-based practice in designing treatment plans and evaluating a patient's progress and response to treatment. Therefore, it is imperative to have reliable measures available to the rehabilitation practitioner to assess and monitor treatment outcomes in patients with neck pain.
Given the demonstrated utility of a cervical-based Fitts' Law motor control paradigm in discriminating old subjects from young, chronic neck pain, and tension type headaches from controls, Fitts Law may potentially be used as a predictive ergonomic tool to assess the effect of ergonomic stressors on the cervical spine. However, to inspire confidence in the utility and validity of a functional assessment tool to be used by physical therapists, chiropractors, ergonomists and kinesiologists, it is important to establish the reliability of the measure. For example, given the variability of chronic symptoms overtime, it is essential to establish the minimum detectable change and the between-day reliability of cervical impairment measures so that meaningful improvements in patients treated for chronic neck pain can be identified. Furthermore, the inclusion of methods for objective and quantitative assessment of dysfunctions in clinical practice is important in order to increase the precision of diagnosis and to enable rational development of rehabilitation methods for specific dysfunctions.
Though the robustness of Fitts' Law as a motor control measure is not in question, the reliability of the experimental protocol and associated equipment used in evaluating performance in a cervical-based Fitts' Law paradigm has yet to be established. Accordingly, the inventors have established a three-dimensional (3D) visual target acquisition system (VTAS), e.g. a 3D-VTAS, which is intended to provide measurements based upon a cervical oriented Fitts' Law paradigm which provides for ease of use, high between-day reliability and validity based upon healthy subject's performance. Additionally, the 3D-VTAS provides for increased data by allowing for determination/verification if there are movement trajectory or target size confounds between the measurements of a subject's performance and hence assessments of both healthy and non-healthy individuals as well as assessments of ergonomic factors etc. Accordingly, subject and ergonomic effects of movement trajectory and target size can be established. Beneficially, 3D-VTAS according to embodiments of the invention provide for quick establishment and configuration providing portable systems as well as fixed systems as well as reconfiguration for assessments of movement trajectory effects and target size performance.
The inventors have established 3D-VTAS according to embodiments of the invention based upon the hypothesis that a 3D-VTAS will provide high measurement reliability across four different dependent variables which are dependent on the movement trajectory alignment with the primary motion axes of the cervical spine. These dependent variables being dwell time (DT), target acquisition time (TAT), time to move off target (TMOT), and error index (EI).
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.